<p>In this article, pure and manganese (Mn)-substituted molybdenum disulfide (Mo_1-xMn_xS₂) nanostructures were synthesized using the hydrothermal method for photocatalytic activity. A number of characterization techniques were employed to examine the impact of Mn incorporation on the morphological, structural, optical, and photocatalytic characteristics of MoS₂. The samples were analyzed using field emission scanning electron microscopy, which revealed an aggregated nanoflower-like structure in the recorded images. X-ray diffraction technique was performed to examine the crystal structure of pure and Mn-doped MoS₂ samples, and the results confirmed the formation of the 2H-MoS₂ polytype in all the as-prepared nanostructures, with a reduction in the average crystallite size by increasing the dopant concentration. Edge-terminated active sites in the Mn-doped samples were indicated by Raman analysis. Also, further investigation of the structure was carried out using Fourier transform infrared spectroscopy, confirming the presence of the characteristic Mo-S band. The elemental composition of pure and Mn-doped MoS₂ nanoflowers (NFs) was verified by energy-dispersive X-ray spectroscopy. Brunaure-Emmett-Teller surface analysis was performed to find out the impact of Mn doping on the surface area. The optical properties were observed through ultraviolet–visible spectroscopy, demonstrating allowed direct transitions with an optical energy bandgap that gradually decreased with increasing Mn concentration. The photocatalytic performance of undoped and Mn-doped MoS₂ NFs was evaluated through the degradation of methylene blue (MB) dye under visible-light irradiation. This study demonstrates that high photocatalytic efficiency (96% MB degradation in 60 min under visible light) is achieved at a low Mn concentration (1.5%), highlighting that controlled Mn incorporation enhances charge separation without excessive doping.</p>